Retrievable vena cava filter

ABSTRACT

A filter device positionable within a blood vessel for trapping emboli in the vessel, the filter device having a head and a plurality of divergent legs each secured at a first end to the head; each leg having one or more hooks at a second end. The hooks can include an expandable and contractible sleeve or hook that provides securing means for the legs and which also allows for easy removal of the filter device.

FIELD OF THE INVENTION

The present invention pertains to the field of intra vena cava filters. In particular, the present invention pertains to retrievable intra vena cava filters. Intra vena cava filters are commonly implanted either temporarily or permanently in patients at risk for blood clotting.

BACKGROUND OF THE INVENTION

Blood clots (emboli) carried in the blood stream often constitute serious threats to health and in some instances, to life itself. The reduction of such clots, or their stabilization and arrest of further migration in the circulatory system of the body, is desiderata constantly motivating the development by the medical profession of new techniques and devices for this purpose. Although emboli moving in other portions of the circulatory system can also present serious problems, development of means for preventing emboli from migrating into the pulmonary circulation from the vena cava has received the primary attention.

One method of capturing emboli is the utilization of filters emplaced in the major blood vessels such as the vena cava. U.S. Pat. No. 4,817,600 to Herms et al. discloses a titanium filter having a plurality of legs joined to a head or nose bead; the legs having a first straight portion, and sharply divergent legs extending therefrom.

SUMMARY OF THE INVENTION

The present invention pertains to an intra vena cava filter implantable temporarily or permanently, and methods for removal thereof. The filter includes struts having tips that engage the wall of the vein or inner surface of another organ to provide positional stability of the filter.

In one embodiment, the struts are made of multiple wires, with the end of each wire sharpened and bent into a hook shape facing a different direction. In another embodiment, the expandable hooks are removed with the filter by reducing the diameter of the hooks. In a further embodiment, the filter includes expandable hooks that fit over the ends of the struts. The hooks function to secure the filter in a vessel, but can be expanded to release the struts, allowing removal of the filter. Methods are provided for subsequent removal of the filters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a front perspective view of an intra vena cava filter according to one embodiment of the invention;

FIG. 2A is a side view of one strut of the filter of FIG. 1;

FIG. 2B is a side view of a strut of another embodiment of intra vena cava filter;

FIG. 2C is a cross-sectional view of the strut of FIG. 2A;

FIG. 3A is a front perspective view of an intra vena cava filter according to another embodiment of the invention.

FIG. 3B is a side view of a strut end and radially contractible sleeve of the filter of FIG. 3A embedded in a vessel wall;

FIG. 3C is a side view of the strut end of FIG. 3B with the radially contractible sleeve in an extended, radially contracted configuration as the strut is removed from a vessel wall;

FIG. 4 is a side view of another embodiment of radially contractible sleeve;

FIG. 5 is a side view of another embodiment of a strut with an expandable hook;

FIG. 6 is a side view of the strut of FIG. 5 with the expandable hook in the expanded configuration in position over the retaining member at the end of the strut;

FIG. 7 is a side view of the strut of FIG. 6 with the expandable hook in a radially contracted configuration secured to the end of the strut and embedded in the caval wall; and

FIG. 8 is a side view of the strut of FIG. 7 with the expandable hook in an expanded configuration to release the strut for removal of the filter.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings wherein like reference numerals refer to like elements throughout the several views, FIG. 1 is a front perspective view of a filter 10 including a hub 12 from which extends a plurality of legs 14. Each leg can be straight or can include bends or curves along its length. Bends or curves in the legs may help catch thrombi that flow through the vessel. In one embodiment, all of the legs 14 are identical. In another embodiment, some or all of the legs 14 are differently shaped. Some legs 14 can be straight while others have one or more bends, and the legs with bends can have different numbers of bends and the angles of the bends can be different. The legs 14 can be biased to expand from a radially compressed configuration in which some or all of the legs 14 are touching within a delivery device to the expanded, cone shaped configuration shown in FIG. 1, when deployed in a blood vessel.

The free end 13 of each leg 14 includes one or more barbs 16 for engagement with the vessel wall to stabilize filter 10 within a vessel. The barbs 16 can be integral with the legs 14 or the barbs 16 can be made separately and then attached to the free ends 13 of the legs 14. In one embodiment, each leg 14 is made of a plurality of wires 18. In the embodiment shown in FIG. 1, each leg 14 is made of three wires 18 attached to each other along their length. Each wire 18 has a barb 16 at the free end 13. The barbs 16 face in opposing directions. In another embodiment, the barbs 16 can face in substantially the same direction but are spaced apart. In a further embodiment, each leg is formed of a single wire that is split or divided into a plurality of barbs at the free end. The barbs 16 are configured to anchor the filter to the vessel walls.

The legs 14 and hub 12 can be made of the same material or can be made of different materials. Suitable materials include metals such as platinum, gold, tantalum, tungsten, titanium, or metal alloys such as stainless steel, Beta III Titanium, cobalt-chrome alloy, Elgiloy®, L605, MP35N, and Ta-10W. In one embodiment, the legs 14 and hub 12 are made of biocompatible titanium alloy beta III (ASTM grade 10, obtained from Ormco Corporation of Glendora, Calif., and designated Ti-11.5Mo-6Zr-4.5Sn, with major alloy elements molybdenum (10-13%), Zirconium (4.5-7.5%) and Tin (3.75-5.25%))

The legs 14 can be made of a plurality of wires, ribbons, threads, rods, filaments, etc. In one embodiment, the legs 14 are made of a bundle of three wires. The wires 18 can be attached along their entire length, as shown in FIGS. 1, 2A and 2C. In another embodiment the wires 18 are attached to each other at one or more discrete points 20 along their length. In the embodiment shown in FIG. 2B, a leg 114 is formed of three wires 18 spaced apart between the attachment points 20. The wires can be attached by adhesive, and solder. In one embodiment, legs 14 are made of wire having a diameter of about 0.018 inch (0.5 mm).

The legs 14 extend outward from the hub 12 to define an imaginary cone. In one embodiment, the hub 12 is formed by fusing the legs 14 together. In a further embodiment, the hub 12 is a separate element attached to the legs 14. The hub 12 can have any shape, including a sphere, cylinder, oval, polygon, etc. In some embodiments, the legs 14 include multiple angles, as shown in FIG. 1. In one embodiment, the diameter of the base of the filter is about 38 mm, and the overall length of the filter is about 50 mm.

In a further embodiment, shown in FIGS. 3A-3C the filter 210 includes radially contractible sleeves 22 attached to one or more legs 214. The radially contractible sleeve 22 fits over the barb 16 and is attached to the free end 113 of the leg 214. The sleeve 22 can be made of a mesh, braid, net, or woven material. As used herein, woven material is intended to include a plurality of strands that are interlaced, twisted, knotted, braided, knitted, or otherwise interconnected to form a material that contracts and expands radially and in a lengthwise direction. In one embodiment, the sleeve 22 is made of Nitinol. In the radially expanded state, shown in FIG. 3B, the sleeve 22 diameter is larger than the diameter of the barb 16. In the radially contracted state, shown in FIG. 3C, the sleeve 22 extends lengthwise and fits tightly around the barb 16. In use, the filter 210 is delivered to the desired vessel location with the sleeves 22 in a radially expanded state covering barbs 16 of the legs 214. The sleeve-covered barbs 16 are embedded in the vessel walls 50 to anchor the filter 210, as shown in FIG. 3B. When the filter 210 is to be retrieved, the legs 214 are pulled, causing the sleeves 22 to extend and radially contract around the extended barbs 16, reducing their diameter and allowing the barbs 16 to be removed from the vessel wall 50, as shown in FIG. 3C. After a filter has been in place for a period of time, endothelial growth over the barbs often makes removal difficult. The ability of the sleeve 22 to radially contract reduces its diameter and allows the filter 210 to be removed even after endothelial growth occurs over the sleeve 22.

In a further embodiment, the radially contractible sleeve 122 has a plurality of projections 26, as shown in FIG. 4. The projections 26 can be extensions of wires, threads, ribbons, etc. that form the net, mesh or woven radially contractible sleeve 122. In another embodiment, the projections 26 are additional wires, threads, ribbons, etc. attached to the exterior of the sleeve 122. The projections 26 may help anchor the sleeve within the vessel wall 50.

Another embodiment of the invention is shown in FIGS. 5-8. This embodiment is similar to the embodiment shown in FIG. 3A except that instead of a barb, the free ends 113 of the legs 414 have a retaining member 116. An expandable hook 222 fits over and is secured to the retaining member 116. The expandable hook 222 anchors the filter to the vessel wall 50, as shown in FIG. 7. The retaining member 116 can be configured as a sphere, as shown in FIGS. 5-8, or any other shape that provides a surface to which the expandable hook 222 can be secured. Other such shapes include a square or other polygon, a triangle, an oval, etc.

The expandable hook 222 is radially expandable and fits over the retaining member 116 at the free end 113 of each leg 414. Once the expandable hook 222 is positioned over the retaining member 116, the hook 222 is radially contracted around the retaining member 116 thereby securing the hook 222 to the leg 414. The expandable hook 222 can be made of a mesh, braid, net, or woven material. In one embodiment, the expandable hook 222 is made of Nitinol. The expandable hook 222 can be expanded and contracted by changing the temperature of the hook. In another embodiment, the expandable hook 222 is mechanically expanded and contracted. In further embodiments, the expandable hook 222 is expanded and contracted via a chemical reaction.

In the radially expanded state, shown in FIGS. 5 and 6, the diameter of the expandable hook 222 is larger than the diameter of the retaining member 116. In the radially contracted state, shown in FIG. 7, the expandable hook 222 extends lengthwise and contracts tightly around the retaining member 116. In use, expandable hooks 222 are attached to retaining members 116 at the free ends 113 of at least two filter legs 414. See FIGS. 5 and 6. The hooks 222 are contracted around the retaining members 116, and the filter is delivered to the desired vessel location where the expandable hooks 222 are embedded in the vessel walls 50, as shown in FIG. 7. If the filter is to be retrieved, the hooks 222 are expanded, as shown in FIG. 8, thereby releasing the retaining members 116 and allowing the filter to be retrieved. The hooks 222 remain in the vessel wall 50.

The filter 10, 210 can be placed within a vessel by way of a jugular vein access point or other intravascular route as known to those skilled in the art. It is anticipated that the filter disclosed herein can be placed permanently in the vena cava or other organ, as well as being placed temporarily.

Numerous characteristics and advantages of the invention covered by this document have been set forth in the foregoing description. It will be understood, however, that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size and ordering of steps without exceeding the scope of the invention. The invention's scope is, of course, defined in the language in which the appended claims are expressed. 

1. A filter device positionable within a blood vessel for trapping emboli, the device comprising: a plurality of divergent legs having first and second ends, wherein the legs are secured at their first ends to each other and each leg has at least two barbs at the second end.
 2. The filter device of claim 1, wherein the legs are formed of nitinol.
 3. The filter device of claim 1, wherein each leg is formed of a plurality of wires, each wire having a barb at the second end of the leg.
 4. The filter device of claim 3, wherein the plurality of wires are attached along their length.
 5. The filter device of claim 1, wherein each leg is formed of three wires bonded together, wherein each wire has an outwardly facing barb at the second end of the leg.
 6. The filter device of claim 5, wherein the wires are bonded together at one or more discrete locations along a length of the leg.
 7. The filter device of claim 6, wherein the wires are spaced apart between the bonded locations.
 8. The filter device of claim 1, wherein each leg includes a first linear portion emanating distally from the first end, a second, multi-angled portion, and a third linear portion including the barbs.
 9. The filter of claim 1, wherein the first ends of the legs are fused together to form an apical head.
 10. The filter of claim 1, further comprising an apical head, wherein the first ends of the legs are attached to the head.
 11. A filter device positionable within a blood vessel for trapping emboli, the device comprising: an apical head; a plurality of divergent legs each secured at a first end to said head, each leg having a separate attachment means at a second end; wherein each of said separate attachment means includes an expandable member.
 12. The filter device of claim 11, wherein the legs are formed of wires.
 13. The filter device of claim 11, wherein each leg includes a first linear portion emanating distally from said head, a second, multi-angled portion, and a third linear portion including the attachment means.
 14. The filter device of claim 11 wherein said expandable member is a radially expandable and contractible sleeve.
 15. The filter device of claim 14, wherein the attachment means further includes a barb disposed at the second end of each leg, wherein the radially expandable and contractible sleeve is disposed over the barb.
 16. The filter device of claim 15, wherein the sleeve is configured such that it radially contracts when a pulling force is exerted on the filter.
 17. The filter device of claim 14, wherein the radially expandable and contractible sleeve includes a plurality of outwardly-extending projections.
 18. The filter device of claim 17, wherein the sleeve is woven and the plurality of projections are formed by cuts in strands forming the weave.
 19. The filter device of claim 11, wherein the attachment means further includes a retaining member disposed at the second end of each leg and the expandable member is an expandable hook configured to be removably attached to the retaining member.
 20. The filter device of claim 19, wherein the retaining member is a sphere disposed at the second end of the leg.
 21. The filter device of claim 19, wherein the expandable hook is configured such that in an expanded state the hook slides over the retaining member, and in a radially contracted state the hook is fixed to the retaining member.
 22. The filter device of claim 19, wherein the expandable hook is woven.
 23. The filter device of claim 19, wherein the expandable hook is made of nitinol.
 24. A method of filtering emboli contained in a blood vessel comprising the steps of: providing a removable filter device having a plurality of divergent legs secured to each other at a first end, each leg having a separate attachment means at a second end, wherein said attachment means includes a radially expandable and contractible member; placing the removable filter device into the blood vessel such that the attachment means secures the filter to a vessel wall; collecting emboli passing through the blood vessel; and removing the filter device and collected emboli from the blood vessel.
 25. The method of claim 24, wherein said filter device is placed within the blood vessel with the radially expandable and contractible members embedded in the vessel wall.
 26. The method of claim 24, wherein said attachment means further includes a barb at the second end of each leg; wherein the radially expandable and contractible member is disposed over the barb such that both the barb and radially expandable and contractible member are embedded in the vessel wall.
 27. The method of claim 26, wherein the radially expandable and contractible member is in an expanded state while embedded in the vessel wall; wherein the step of removing the filter device includes exerting a pulling force on the legs, causing the expandable and contractible members to radially contract, reducing their diameter and aiding removal of the filter device.
 28. The method of claim 24, wherein the attachment means further includes a retaining member at the second end of the legs, wherein the radially expandable and contractible member is an expandable hook; wherein the step of placing the filter into a blood vessel includes expanding the expandable hook and placing at least a portion of the hook over the retaining member, radially contracting the expandable hook around the retaining member, and placing the filter into the blood vessel such that the expandable hook is embedded in the vessel wall.
 29. The method of claim 28, wherein the step of removing the filter includes radially expanding the expandable hook to release the retaining member and removing the filter, wherein the expandable hook remains in the vessel wall.
 30. A blood clot capturing device for implantation in a blood vessel comprising: a plurality of legs, each leg having a first end and a second end; a plurality of divergent hooks formed at the second end of each leg; wherein the legs are connected to each other at their first ends.
 31. A retrievable vena cava filter comprising: a plurality of elongate legs having first and second ends, the first ends of the legs connected to each other, and the second ends having a retaining member; a plurality of expandable hooks having first and second ends, one hook disposed on each retaining member; wherein the expandable hooks are configured such that in an expanded state, the first ends of the hooks fit over the retaining members; in a contracted state, the first ends of the hooks contract around the retaining members to secure the hooks to the legs and the second ends of the hooks are configured to pierce a vessel wall.
 32. A retrievable vena cava filter comprising: an apical head; a plurality of elongate legs diverging from the head, each leg having at least one barb at a free end of the leg; and a plurality of contractible sleeves, one sleeve disposed on each barb.
 33. The filter of claim 32, wherein the legs are made of stainless steel.
 34. The filter of claim 32, wherein the legs are made of a shape-memory material.
 35. The filter of claim 32, wherein the shape-memory material is a nickel-titanium alloy.
 36. The filter of claim 32, wherein the barb is configured to pierce a vessel wall. 